1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type magnetic transducer and to a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein a track width, that is, the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface, is reduced down to microns or the submicron order. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to FIG. 19A to FIG. 22A and FIG. 19B to FIG. 22B to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 19A to FIG. 22A are cross sections each orthogonal to an air bearing surface of the thin-film magnetic head. FIG. 19B to FIG. 22B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 19A and FIG. 19B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 35 to 60 nm, for example, through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 having a thickness of about 35 to 60 nm, for example, is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 2.5 to 3.5 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 20A and FIG. 20B, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 to 0.25 xcexcm, for example, is formed on the bottom pole layer 108. Next, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. Next, a photoresist layer 110 having a thickness of 1.0 to 1.5 xcexcm, for example, is formed on top of a region of the recording gap layer 109 where a thin-film coil described later is to be formed. On the photoresist layer 110, the thin-film coil 111 for an induction-type recording head is formed through electrolytic plating, for example. A photoresist layer 112 is then formed to cover the thin-film coil 111.
Next, as shown in FIG. 21A and FIG. 21B, a top pole layer 113 made of a magnetic material and having a thickness of 2.0 to 3.0 xcexcm, for example, is formed for the recording head in a region extending from the top of a portion of the recording gap layer 109 located in the pole portion, through the top of the photoresist layer 112 to the contact hole 109a. 
Next, as shown in FIG. 22A and FIG. 22B, a portion of the recording gap layer 109 around the top pole layer 113 is removed and the bottom pole layer 108 is etched by only 0.3 to 0.4 xcexcm, for example, through ion milling, for example, using the top pole layer 113 as a mask. As shown in FIG. 22B, the structure is called a trim structure wherein the sidewalls of the top pole portion (the top pole layer 113), the recording gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an overcoat layer 114 of alumina, for example, is formed to cover the top pole layer 113. Finally, lapping of the slider is performed to form the air bearing surface 120 of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head is thus completed.
In FIG. 22A, the throat height is indicated with xe2x80x98THxe2x80x99, the zero throat height position with xe2x80x98TH0xe2x80x99, the MR height with xe2x80x98MR-Hxe2x80x99, and the apex angle with xcex8. The throat height is the length (height) of pole portions, that is, portions of magnetic pole layers facing each other with a recording gap layer in between, the length between the air-bearing-surface-side end and the other end. The zero throat height position is the position of an end of a pole portion opposite to the air bearing surface. The MR height is the length (height) between the air-bearing-surface-side end of the MR element 105 and the other end. The apex is a hill-like raised portion of the coil covered with an insulating layer such as the photoresist layer 112. The apex angle is the angle formed between the top surface of the recording gap layer 109 and the slope of the apex on a side of the pole. In the thin-film magnetic head shown in FIG. 22A, zero throat height position TH0 is the position of an end of the photoresist layer 112 on a side of the air bearing surface 120.
FIG. 23 is an explanatory view for illustrating the relationship between a top view (an upper view of FIG. 23) of the main part of the thin-film magnetic head shown in FIG. 22A and FIG. 22B and a cross-sectional view (a lower view of FIG. 23) thereof. The overcoat layer 114 and some of the other insulating layers and insulating films are omitted in FIG. 23. In FIG. 23, xe2x80x98P2Wxe2x80x99 indicates the recording track width.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, and apex angle xcex8 as shown in FIG. 22A, and recording track width P2W as shown in FIG. 23.
To achieve high surface recording density, that is, to fabricate a recording head with a narrow track structure, it has been particularly required that track width P2W fall within the submicron order of 1.0 xcexcm or less. It is therefore required to process the top pole of the submicron order through semiconductor process techniques.
A problem is that it is difficult to form the top pole layer of small dimensions on the apex.
As disclosed in Published Unexamined Japanese Patent Application Hei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied to the top of the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 xcexcm or more. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm over the apex, a photoresist film having a thickness of 8 to 10 xcexcm or more, for example, is formed below the apex since the fluid photoresist goes downward.
To implement a recording track width of the submicron order as described above, it is required to form a frame pattern having a width of the submicron order through the use of a photoresist film. Therefore, it is required to form a fine pattern of the submicron order on top of the apex through the use of a photoresist film having a thickness of 8 to 10 xcexcm or more. However, it is extremely difficult to form a photoresist pattern having such a thickness into a reduced pattern width, due to restrictions in a manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the base electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may go out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern.
In the region on the slope of the apex, in particular, the rays reflected off the base electrode film include not only vertical reflected rays but also rays in slanting directions and rays in lateral directions from the slope of the apex. As a result, the photoresist is exposed to those reflected rays of light and the photoresist pattern more greatly goes out of shape.
With regard to the track width, it is required that the amount of lapping the slider will not affect the track width.
Therefore, when the top pole layer is formed on the apex, some means is required for reducing the effect on the track width of the rays reflected off the base electrode film during exposure of the photolithography process.
The greater apex angle xcex8, the greater is the amount of rays of light reflected off the base electrode film moving in the slanting or lateral direction. As a result, the track width is susceptible to those reflected rays. Therefore, apex angle xcex8 is reduced in prior art by increasing the distance between zero throat height position TH0 and the outermost end of the thin-film coil 111, for example.
A problem of a prior-art thin-film magnetic head is that it is difficult to reduce the magnetic path (yoke) length. That is, if the coil pitch is reduced, a head with a reduced yoke length is achieved and a recording head having an excellent high frequency characteristic and an excellent nonlinear transition shift (NLTS) characteristic is achieved, in particular. However, if the coil pitch is reduced to the limit, the distance between the outermost end of the coil and the zero throat height position, and the distance between the innermost end of the coil and the portion in which the top and bottom pole layers are in contact with each other are major factors that prevent a reduction in yoke length. This problem will now be described in detail.
In the thin-film magnetic head shown in FIG. 22A and FIG. 22B, for example, the thin-film coil 111 is formed on the photoresist layer 110. The neighborhood of an end of the photoresist layer 110 is rounded. In such a portion it is impossible to etch the seed layer of the coil, and the coil is thereby shorted. The thin-film is therefore required to be formed on a flat portion. Consequently, it is required that each of the outermost and innermost ends of the coil 111 is located at a certain distance from each of the outermost and innermost ends of the photoresist layer 110, respectively. Furthermore, since the photoresist layer 112 is formed to cover the coil 111, the distance between the outermost end of the coil 111 and the outermost end of the photoresist layer 112, that is, the distance between the outermost end of the coil 111 and the zero throat height position, is greater than the distance between the outermost end of the coil 111 and the outermost end of the photoresist layer 110. In addition, the distance between the innermost end of the coil 111 and the innermost end of the photoresist layer 112, that is, the distance between the innermost end of the coil 111 and the portion in which the top and bottom pole layers are in contact with each other, is greater than the distance between the innermost end of the coil 111 and the innermost end of the photoresist layer 110. The distance between the outermost end of the coil 111 and the outermost end of the photoresist layer 112, and the distance between the innermost end of the coil 111 and the innermost end of the photoresist layer 112 thus described are the factors that prevent a reduction in the yoke length.
Furthermore, the yoke length is made greater if the distance between the outermost end of the coil 111 and zero throat height position TH0 is increased in order to reduce apex angle xcex8 as described above.
FIG. 24 is an enlarged view of portion A of FIG. 23, that is, the neighborhood of the innermost end of the thin-film coil 111. Assuming that the coil thickness is 2 to 2.5 xcexcm, and the thickness of each of the photoresist layer 110 and a portion of the photoresist layer 112 located above the top surface of the coil 111 is 1 to 2 xcexcm, length d1 between the innermost end of the coil 111 and the innermost end of the photoresist layer 110 is required to be 3 xcexcm, for example, as shown in FIG. 24. Length d2 between the innermost end of the coil 111 and the innermost end of the photoresist layer 112 is required to be 5 xcexcm, for example.
Furthermore, if apex angle xcex8 is 25 to 35 degrees, the distance between the outermost end of the coil 111 and the outermost end of the photoresist layer 112 is required to be 10 xcexcm, for example. Assuming that the thin-film coil 111 is a single-layer eight-turn coil in which the line width is 1.2 xcexcm and the space is 0.8 xcexcm, the portion of the yoke length corresponding to the coil 111 is 15.2 xcexcm. In addition to this length, a length of 10 xcexcm, for example, that is, the distance between the outermost end of the coil 111 and the outermost end of the photoresist layer 112, and a length of 5 xcexcm, for example, that is, the distance between the innermost end of the coil 111 and the innermost end of the photoresist layer 112 are required for the yoke length. Therefore, the yoke length is 30.2 xcexcm, for example. In the present patent application, the yoke length is the length of a portion of the pole layer except the pole portion and the contact portions, as indicated with L0 in FIG. 22A. As thus described, it is difficult in the prior art to further reduce the yoke length, which prevents improvements in high frequency characteristic and NLTS.
Although the example in which the single-layer thin-film coil is formed has been described so far, the problem that it is difficult to reduce the yoke length similarly applies to the case in which a two-layer coil is formed. That is, in the prior art, the second layer of the coil is formed on the photoresist layer covering the first layer of the coil. Therefore, it is required that each of the outermost and innermost ends of the second layer of the coil is located at a certain distance from a rounded end of the photoresist layer.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for achieving reductions in track width and yoke length of an induction-type magnetic transducer.
A thin-film magnetic head of the invention comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. One of the magnetic layers includes: a first layer located in a region facing toward the at least part of the thin-film coil; and a second layer connected to a surface of the first layer facing toward the thin-film coil, the second layer including one of the pole portions. The second layer includes a first portion located closer to the medium facing surface and a second portion located farther from the medium facing surface. The first portion is smaller than the second portion in width. The at least part of the thin-film coil is located on a side of the second layer. The other of the magnetic layers has a portion that defines a track width. The head further comprises: an insulating layer encasing portion formed in the second layer and provided for encasing an insulating layer for defining a throat height; and the insulating layer for defining the throat height placed in the encasing portion.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers.
The method of the invention includes the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the thin-film coil such that the at least part of the coil is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The step of forming one of the magnetic layers includes the steps of: forming a first layer located in a region facing toward the at least part of the thin-film coil; and forming a second layer connected to a surface of the first layer facing toward the thin-film coil, the second layer including one of the pole portions. The second layer is formed in the step of forming the second layer such that the second layer includes a first portion located closer to the medium facing surface and a second portion located farther from the medium facing surface, the first portion being smaller than the second portion in width. The at least part of the thin-film coil is located on a side of the second layer in the step of forming the coil. A portion that defines a track width is formed in the step of forming the other of the magnetic layers. The method further includes the steps of: forming an insulating layer encasing portion in the second layer, the encasing portion being provided for encasing an insulating layer for defining a throat height; and forming the insulating layer for defining the throat height in the encasing portion.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the throat height is defined by the insulating layer encasing portion formed in the second layer of one of the magnetic layers. The track width is defined by the other of the magnetic layers. In the invention at least a part of the thin-film coil is located on a side of the second layer. As a result, it is possible that the other of the magnetic layers that defines the track width is formed on the flat surface with accuracy. In the invention the second layer includes the first portion located closer to the medium facing surface. The first portion has the width smaller than the width of the second portion located farther from the medium facing surface. It is thereby possible to prevent an increase in effective track width. According to the invention, it is possible that an end of at least a part of the thin-film coil is located near an end of the second layer. A reduction in yoke length is thereby achieved.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, an insulating layer may be further provided. The insulating layer covers the at least part of the thin-film coil located on the side of the second layer, and has a surface facing toward the gap layer that is flattened together with a surface of the second layer facing toward the gap layer.
According to the head or the method of the invention, the other of the magnetic layers may be made up of one layer.
According to the head or the method of the invention, the other of the magnetic layers may include: a pole portion layer including the other of the pole portions; and a yoke portion layer forming a yoke portion and connected to the pole portion layer. In this case, an end face of the yoke portion layer facing toward the medium facing surface may be located at a distance from the medium facing surface. The thin-film coil may include: a first layer portion located on a side of the second layer of the one of the magnetic layers; and a second layer portion located on a side of the pole portion layer of the other of the magnetic layers. In this case, a first insulating layer and a second insulating layer may be provided. The first insulating layer covers the first layer portion of the coil and has a surface facing toward the gap layer, the surface being flattened together with a surface of the second layer facing toward the gap layer. The second insulating layer covers the second layer portion of the coil and has a surface facing toward the yoke portion layer, the surface being flattened together with a surface of the pole portion layer facing toward the yoke portion layer.
According to the head or the method of the invention, the first portion of the second layer may include a portion that is closest to the gap layer and has a width equal to the track width.
According to the head or the method of the invention, a magnetoresistive element, and a first shield layer and a second shield layer may be further provided. The first and second shield layers are provided for shielding the magnetoresistive element. Portions of the first and second shield layers located in regions on a side of the medium facing surface are opposed to each other, the magnetoresistive element being placed between the portions of the shield layers.
Other and further objects, features and advantages of the invention will appear more fully from the following description.